Teleop_joy and SITL

rdehart · October 21, 2020, 4:48pm

Hi, I am attempting to control a SITL instance of the BlueROV2 via mavlink and the teleop_joy project found here:

I am using an XBox controller and I have edited the launch file to match what I see in /dev/. I can arm and set modes via the controller just fine, it’s just the actual movement I dont see in gazebo.

Since I am also running the bluerov playground I can see the topics in /joy change when I move the joysticks. Also there are topics under /BlueROV and /mavros I can see and they seem to be similar values, but /BlueROV is slower to update. What is the difference between these two?

patrickelectric · October 22, 2020, 12:24pm

Hi,

Are you talking about the gazebo simulation in bluerov-ros-playground ? For that you’ll need to run SITL running, can you check if the /mavros topics are all updated ? Can you connect QGC without bluerov-ros-pkg ?

rdehart · October 22, 2020, 6:59pm

Its connecting now. Not sure why it did not earlier. It does state “Parameters are missing from firmware COMPASS_PRIMARY”

patrickelectric · October 23, 2020, 11:37am

It may be a problem related to the firmware version that you running, but you can set the first compass as primary.

rdehart · October 27, 2020, 6:48pm

OK, I got QGC to communicate with the joystick and SITL by changing its SYSID_MGCS=1 rather than 255. It was actually 254 at first, and Im not sure why.

This brings me to 3 questions:

The teleop_joy project mentioned earlier does not seem to set SYSID_MGCS at any time. Perhaps that is why it is not working?

I reviewed the blue_rov_playground code found below, and I cant find it there either.

Finally, in said code, in pubs.py, line 102, it seems to be continuously sending [1201, 1200, 1200, 1200, 1200, 1200, 1200, 1205] to mavros/rc/override. WHY?? See here:

github.com

patrickelectric/bluerov_ros_playground/blob/master/src/bluerov/pubs.py

#!/usr/bin/env python
"""Publish data to ROS topic
"""
import mavros_msgs.msg
import rospy
import time


class Pubs(object):
    """Class that control publish data to ROS

    Attributes:
        data (dict): Dict that contains all data available of all topics
        topics (list): list of topics structs
    """
    def __init__(self):
        # Dict with all data
        self.data = {}
        # Get data from topic list
        self.topics = []

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rdehart · October 27, 2020, 6:52pm

Interestingly, the gazebo_sitl.launch file actually specifies the sys ID:

But Im not sure then why I had to make GCS sysid 1

github.com

patrickelectric/bluerov_ros_playground/blob/master/launch/gazebo_sitl.launch

<?xml version="1.0"?>
<launch>
    <arg name="log_output" default="log"/>
    <arg name="model" default="$(find bluerov_ros_playground)/model/BlueRov2.urdf.xacro"/>

    <arg name="fcu_url" default="udp://:14551@127.0.0.1:14549"/>
    <arg name="gcs_url" default="udp://:14549@127.0.0.1:14548"/>
    <arg name="system_id" default="255"/>
    <arg name="component_id" default="240"/>
    <arg name="tgt_system" default="1"/>
    <arg name="tgt_component" default="1"/>
    <arg name="pluginlists_yaml" value="$(find bluerov_ros_playground)/launch/mav_pluginlists.yaml"/>
    <arg name="config_yaml" value="$(find mavros)/launch/apm_config.yaml"/>

    <!-- Launch Gazebo with underwater world -->
    <include file="$(find gazebo_ros)/launch/empty_world.launch">
        <arg name="paused" value="false"/>
        <arg name="world_name" value="$(find freefloating_gazebo)/world/underwater.world"/>
    </include>

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patrickelectric · October 28, 2020, 1:09pm

The teleop_joy project mentioned earlier does not seem to set SYSID_MGCS at any time. Perhaps that is why it is not working?

teleop_joy is a generic ROS service, there is no connection with MAVLINK related protocol or interface.

Pubs is a class that is used to abstract ROS publications, if you run the Pubs class it’ll execute the test script in the bottom, that as you saw, will set all channels to 1200.

The Ground Station ID only needs to be configured when multiple softwares are controlling the ROV at the same time, like the mavlink code that does the bridge between mavlink-ROS and QGC.

rdehart · October 28, 2020, 1:32pm

“The Ground Station ID only needs to be configured when multiple softwares are controlling the ROV at the same time, like the mavlink code that does the bridge between mavlink-ROS and QGC.”

Thank you! Where does the mavlink-ROS bridge actually set the SYSID? I looked for it and cannot find it.

Also, I could not find where the bridge or associated classes sent heartbeat signals.

patrickelectric · October 28, 2020, 1:58pm

This is done by mavros directly.

rdehart · October 28, 2020, 2:13pm

OK!

rdehart · November 10, 2020, 9:16pm

Ive reviewed mavros and your bridge and I was wondering

Is there a reason why you used pymavlink and pyros to write your own bridge instead of using mavros?

Is there something in mavros that means I should avoid using it?

rdehart · December 10, 2020, 7:22pm

The bridge doesnt use mavros, does it?

patrickelectric · December 14, 2020, 4:28pm

Hi @rdehart,

Yes it does, you can check the usage of mavros here, for more information check the README.

You can run the same code without ROS.

rdehart · December 14, 2020, 6:33pm

Ah, I should clarify. The bridge doesn’t call mavros functions, does it?

patrickelectric · December 15, 2020, 2:15pm

Hi @rdehart,

mavros is a ros package, it is like a service that provides mavlink messages via ros topics. There is no need to call functions of the package, the only that is being used is the mavlink abstraction from mavros and the information for the mavros specific messages.

rdehart · December 27, 2020, 10:59pm

So is the bridge acting as a GCS? This goes back to my heartbeat question (see above). If I post a ROS topic that sends a rcoverride command via the bridge, I have to be a GCS, right? And if so, I have to be sending heartbeats?

rdehart · January 19, 2021, 3:05am

OK, I think I have answered the previous question for myself now.

However, I dont fully understand WHEN one should launch with user_mav.launch and when one should launch with bluerov2_node.launch. In fact, it would seem that both user_mav.launch and bluerov2_node.launch eventually call user.py as “user_node”. The Readme provides no clarification if one is supposed to be run when SITL is running only, or if the blue rov is running only, which is what I suspect.

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